Polymers stabilized with bis-heterocyclic benzoates

ABSTRACT

The invention relates to bis-heterocyclic benzoate compounds which have been found to be extremely effective ultraviolet stabilizers. The invention also relates to ultraviolet degradable organic compositions containing an amount of a bis-heterocyclic benzoate composition to prevent such degradation. These stabilizers are effective in the presence of other additives commonly employed in polymeric compositions including, for example, pigments, colorants, fillers, reinforcing agents and the like. These ultraviolet stabilizers may also be incorporated into the organic compositions such as polymers by adding to the polymer melt or dissolved in the polymer dope, coated on the exterior of the shaped or molded article, film or extruded fiber.

This is a division of Application Ser. No. 484,843 filed July 1, 1974,now U.S. Pat. No. 3,963,738.

This invention relates to ultraviolet stabilizers and their use inorganic compositions. More particularly, the invention relates tobis-heterocyclic benzoate compositions and the stabilization of organiccompositions against deterioration resulting from the exposure to lightwith such bis-heterocyclic benzoate compositions.

The degradative effects of ultraviolet light on various organiccompositions is well known in the art. The photo-deterioration ordegradation is of particular concern with organic photo-degradablecompositions which are exposed to ultraviolet light, such as sunlight,for long periods of time. One group of such photo-degradable organiccompositions is polymeric compositions such as polyolefins, polyestersand the like. On exposure to sunlight for extended periods of time,these polymeric compositions degrade and their physical properties arereduced to render the polymeric composition less useful for mostapplications. Therefore, considerable effort has been directed toproviding a solution to the photo-degradation problem of polymericcompositions. As a result of this effort, there have been discoveredmany additives and stabilizers which improve the stability of polymericcompositions.

Moreover, various additives and stabilizers exhibit the power to absorbelectromagnetic radiation within the band of 2900 to 4000 A. and whenincorporated in various plastic materials such as transparent sheets,the resultant sheet acts as a filter for all of the radiation passingthrough and will transmit only such radiations as are not absorbed bythe sheet and/or the absorbing agent. It is thus possible to screen outundesirable radiations and utilize the resulting transparent sheet as afilter in many technical and commercial applications such as wrappingsfor food products and the like.

While there are many additives, stabilizers and mixtures thereof whichare known in the art to improve the ultraviolet light stability oforganic compositions, there is a need in the art for more efficient andeffective stabilizers to prevent the photo-degradation of organiccompositions susceptible to photo-degradation. Therefore, to provide amore effective and efficient ultraviolet stabilizer for organiccompositions susceptible to such degradation would be an advance in thestate of the art.

It is therefore an object of the present invention to providecompositions characterized by improved resistance to degradation anddeterioration by ultraviolet radiation.

Another object of the present invention is to provide compositionscontaining bis-heterocyclic benzoate compositions which are resistant toultraviolet degradation.

A further object of this invention is to provide processes for improvingthe resistance of organic materials to deterioration and degradation byactinic radiation and especially ultraviolet radiation.

It is a still further object of this invention to provide compositionsand processes for improving the resistance of organic materials todeterioration and degradation by actinic radiations including shortwave-length visible radiations.

Further objects and advantages of the invention will be apparent tothose skilled in the art from the accompanying disclosure and claims.

In accordance with the present invention, organic compositions areprovided which are useful as ultraviolet stabilizers. These organiccompositions contain a bis-heterocyclic phenyl group connected through acarboxyl group to aromatic rings, which by the "photo-Fries"rearrangement can form hydroxyl groups. The organic compositions of thepresent invention are aryl esters of heterocyclic aromatic acids havingthe following structure: ##STR1## wherein A is a group having thestructure ##STR2## wherein Z is an oxygen atom, a sulfur atom, or anitrogen atom containing a hydrogen atom or a substituted orunsubstituted lower alkyl group having 1 to 12 carbon atoms;

R₁ and R₂ are hydrogen, lower alkyl, substituted lower alkyl,cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, loweralkylaryl, aryl-substituted-aryl, chloro, bromo, alkoxy, alkylsulfonyl,substituted amino, cyano, and at least two adjacent R₁ or R₂substituents, combined with the carbon atoms to which they are attached,are joined alkylene groups completing a carbocyclic ring which ring canbe substituted with any of the substituents listed above for R₁ or R₂.

B is an aryl group having the formula ##STR3## wherein R₃, R₄, R₅, R₆and R₇ are hydrogen, lower alkyl, substituted lower alkyl, cycloalkyl,substituted cycloalkyl, aryl, substituted aryl, lower alkylaryl,aryl-substituted-aryl, alkoxy, hydroxy, substituted amino, carboalkoxy,nitrile, chloro, bromo and the substituents R₃ and R₄, R₄ and R₅, R₅ andR₆ and R₆ and R₇, combined with the carbon atoms to which they areattached, are joined alkylene groups completing a carbocyclic ring whichcan be substituted with any of the substituents listed above for R₃, R₄,R₅, R₆ and R₇.

Suitable A groups having the formula ##STR4## are, for example,substituted and unsubstituted 2,5-diphenyl-1,3,4-oxadiazoldiyl,2,5-diphenyl-1,3,4-thiadiazol-diyl, and 2,5-diphenyl-1,3,4-triazol-diyl.

Examples of suitable diphenyloxadiazol-diyl moieties are those havingthe formula ##STR5## such as 2,5-diphenyl-1,3,4-oxadiazol-3',3"-diyl;2,5-diphenyl-1,3,4-oxadiazol-4',4"-diyl;2,5-diphenyl-1,3,4-oxadiazol-3'4"-diyl;2,5-diphenyl-3',3"-dibromo-1,3,4-oxadiazol-4',4"-diyl;2,5-diphenyl-3'-methoxy-1,3,4-oxadiazol-4',4"-diyl;2,5-diphenyl-3'-methyl-1,3,4-oxadiazol-4',3"-diyl;2,5-diphenyl-3',3",6',6"-tetrabromo-1,3,4-oxadiazol-4',4"-diyl; and2,5-diphenyl-3',3",6',6"-tetramethoxy-1,3,4-oxadiazol-4',4"-diyl.

Examples of suitable diphenylthiadiazol-diyl moieties are those havingthe formula: ##STR6## such as 2,5-diphenyl-1,3,4-thiadiazol-3',3"-diyl;2,5-diphenyl-1,3,4-thiadiazol-4',4"-diyl;2,5-diphenyl-1,3,4-thiadiazol-3',4'-diyl;2,5-diphenyl-3',3"-dibromo-1,3,4-thiadiazol-4',4"-diyl;2,5-diphenyl-3',3"-dichloro-1,3,4-thiadiazol-4',4"-diyl;2,5-diphenyl-3'-methoxy-1,3,4-thiadiazol-4',4"-diyl;2,5-diphenyl-3'-methyl-1,3,4-thiadiazol-4',3"-diyl;2,5-diphenyl-3',3",6',6"-tetrabromo-1,3,4-thiadiazol-4',4"-diyl; and2,5-diphenyl-3',3",6',6"-tetramethoxy-1,3,4-oxadiazol-4',4"-diyl.

Examples of suitable diphenyltriazol-diyl moieties are those having theformula: ##STR7## wherein Q is hydrogen or a substituted orunsubstituted lower alkyl group containing 1 to 12 carbon atoms, such as1-methyl-2,5-diphenyl-1,3,4-triazol-4',4"-diyl;1-methyl-2,5-diphenyl-3',3"-dibromo-1,3,4-triazol-4',4"-diyl;1-methyl-2,5-diphenyl-3'-methoxy-1,3,4-triazol-4',4"-diyl;1-benzyl-2,5-diphenyl-1,3,4-triazol-4',4"-diyl;1-benzyl-2,5-diphenyl-1,3,4-triazol-3',3"-diyl;1-benzyl-2,5-diphenyl-3',3",6',6"-tetrabromo-1,3,4-triazol-4',4"-diyl;1-ethyl-2,5-diphenyl-1,3,4-triazol-3',4"-diyl;1-ethyl-2,5-diphenyl-3',3"-dichloro-1,3,4-triazol-4',4"-diyl;1-ethyl-2,5-diphenyl-3',3"-dimethyl-1,3,4-triazol-4',4"-diyl;2,5-diphenyl-1,3,4-triazol-4',4"-diyl; and2,5-diphenyl-1,3,4-triazol-3',3"-diyl.

Examples of aryl B components having the formula: ##STR8## are2,4-dimethoxyphenyl, 3-methoxyphenyl, 3-methylphenyl, 4-octylphenyl,4-dodecylphenyl, 3-octylphenyl, 2,4-dichlorophenyl, 4-methoxyphenyl,2,4-di-t-butylphenyl, 3-(2-ethylhexyloxy)phenyl, 3-dodecyloxyphenyl,4-cyanophenyl, 4-bromophenyl, 3-hydroxyphenyl and 3-cyclohexylphenyl.The aryl B components can be the same or different.

The bis-heterocyclic benzoate esters can be prepared by reacting thebis-acid chloride with a phenol. For example, one such group of organiccompounds useful as ultraviolet stabilizers is bis-heterocyclic benzoateester-based compositions having the formula ##STR9## These organiccompounds can be prepared according to the following procedure:##STR10## Substituents R₃ through R₇ are defined hereinabove. It isnecessary that at least one of R₃ or R₇ be hydrogen so that, on exposureto ultraviolet light, the aryl ester of the heterocyclic aromatic acidis capable by the "photo-Fries" rearrangement of forming a phenol groupin that position formerly joined through an oxygen atom to the carbonyllinking group, as for example ##STR11##

The oxadiazole, thiadiazole and triazole ring systems are generallyprepared by procedures discussed and references noted in "HeterocyclicCompounds", R. C. Elderfield, Ed., Wiley, New York, pp. 384-626. Thefollowing procedures illustrate typical reaction sequences: ##STR12##

The acid chlorides (I) were prepared by reaction of the correspondingacid [See Zh. Obshch. Khim., 38, 100 1-5 (1968); Chem. Abstr. 69, 96568(1968)] with freshly distilled phenyl chloride [See J. Chem. Soc. 101,2476 (1912)]. The phenols were obtained from commercial sources, or wereprepared by standard methods; a critical requirement is that one of thepositions adjacent to the phenolic hydroxyl group be unsubstituted. Itis believed that the "photo-Fries" rearrangement can occur uponultraviolet exposure of the esters III and that these rearrangementproducts IV are effective stabilizers.

The bis-heterocyclic benzoate compositions can be added to organiccompositions which are susceptible to ultraviolet degradation. Suchcompositions include, for example, polymeric compositions such aspolyester fiber and moldable compositions, such as poly(ethyleneterephthalate), poly(tetramethylene terephthalate) and the like;unsaturated polyesters; polyolefins such as, for example, high, mediumand low density polyethylene, polypropylene, polybutene and the like;polyamides such as nylon 6, nylon 66 and the like; polycarbonates;poly(vinyl chloride); cellulose esters; cellulose ethers;acrylic/butadiene/styrene plastics; acrylics such as poly(methylmethacrylate); polystyrene; gelatin. Such compositions also includenatural and synthetic rubbers such as polybutadiene, and unsaturatedorganic compositions such as oils and the like, as well as compositionscontaining such organic compositions.

The bis-heterocyclic benzoate compositions as effective ultravioletstabilizers or screening agents are generally used in an amount of from0.01 to 10%, by weight, based on the weight of the organic material towhich they are added. While a detectable amount of ultraviolet screeningand stabilization may be obtained with amounts less than 0.01%, thisamount of stabilization or screening would be of little practicalutility in a commercial application. Moreover, while amounts greaterthan 10%, by weight, provide effective ultraviolet stability andscreening, such concentrations are undesirable because of cost and thedeleterious effect which such concentrations may have on the mechanicalproperties of the organic composition in which the stabilizer isincorporated. Preferably, the stabilizer is used in an amount of fromabout 0.1 to about 5%, by weight. For example, an amount of 2%, byweight, of the stabilizer effectively stabilizes cellulose acetatebutyrate plastic compositions.

The ultraviolet stabilized organic compositions of the present inventionmay also contain other additives, pigments, colorants, stabilizers andthe like. For example, polymeric compositions, such as polyolefins, mayalso contain and generally do contain other additives such as white orcolored pigments or colorants, antioxidants, plasticizers, flow aids,processing aids, polymeric modifiers and the like.

These bis-heterocyclic benzoate ultraviolet stabilizers may beincorporated into organic compositions by melt-blending or may be addedonto the surface of an organic plastic material prior to being moldedinto a suitable object, or added to the surface of the molded object.These materials can also be added to coatings and the like which can beapplied to the surface of a molded object.

This invention will be further illustrated by the following examples,although it will be understood that these examples are included merelyfor purposes of illustration and are not intended to limit the scope ofthe invention.

EXAMPLE 1 Di-3-methoxyphenyl2,5-diphenyl-1,3,4-oxadiazol-4',4"-dicarboxylate ##STR13##

A solution of 3.2 g. hydrazine in 50 ml. dimethylformamide (DMF) wasadded in 30 minutes to a 120° mixture of 50 g. dimethyl terephthalate in300 ml. DMF. After stirring for 1 hour, the mixture was poured into 1000ml. water and the crude dihydrazide collected by filtration.Recrystallization was from DMF/water. Heating the dihydrazide (30 g.) in200 ml. polyphosphoric acid at 200°, followed by pouring onto ice andheating on a steam bath, gave 12 g. of the intermediate oxadiazoledi-acid. Heating the acid (12 g.) with thionyl chloride (50 ml.),removal of excess thionyl chloride by distillation and reaction with 10g. 3-methoxyphenol in 100 ml. o-dichlorobenzene gave 12 g. of thesubject compound, a light tan solid.

EXAMPLE 2 Di-2,4-di-t-butylphenyl2,5-diphenyl-1,3,4-oxadiazol-4',4"-dicarboxylate

Reaction of the acid (12 g.) prepared as in Example 1 with thionylchloride, followed by reaction in o-dichlorobenzene with 15 g.2,4-di-t-butylphenol afforded, after recrystallization from methylcellosolve, 12 g. nearly colorless product.

EXAMPLE 3 Di-4-tert-octylphenyl2,5-diphenyl-1,3,4-oxadiazol-4',4"-dicarboxylate

Reaction of the acid (12 g.) prepared as in Example 1 with thionylchloride, followed by reaction in o-dichlorobenzene with 30 g.4-tert-octylphenol afforded, after recrystallization from o-xylene, 18g. colorless product.

EXAMPLE 4 Di-3-methoxyphenyl2,5-diphenyl-1,3,4-thiadiazol-4',4"-dicarboxylate

A mixture of the dihydrazide (30 g.) prepared as in Example 1, andphosphorus pentasulfide was heated at 220° C./10 mm. pressure, followedby cooling and stirring on a steam bath in 4% sulfuric acid (300 ml.).Filtration, water-washing and drying afforded 16 g. of the intermediatethiadiazole di-acid. The acid (16 g.) was reacted with 75 ml. thionylchloride, followed by distillation to remove excess thionyl chloride.Reaction of the resulting di-acid chloride with 15 g. 3-methoxyphenol in250 ml. o-dichlorobenzene gave, after recrystallization from methylcellosolve, 22 g. nearly colorless solid.

Other bis-heterocyclic benzoate compounds, such as bis-oxadiazoles,bis-thiadiazoles and bis-thiazoles, can be prepared by this procedure byusing the appropriate acids and substituted or unsubstituted phenols.Weathering data obtained by the use of several such bis-heterocyclicbenzoate compounds is shown in the following table.

    ______________________________________                                        Typical Weathering Data for 1/16" Thick Poly(tetra-                           methylene terephthalate) Flat Bars Containing 1% of                           The Compounds of this Invention                                               ______________________________________                                                        Flatwise Impact Strength                                                      After Mercury Lamp Exposure                                                   For Hours Indicated                                           ______________________________________                                        Compound          0        300      500                                       ______________________________________                                        Di-3-methoxyphenyl 2,5-di-                                                    phenyl-1,3,4-oxadiazol-                                                       3',3"-dicarboxylate                                                                             18       18       18                                        Di-2,4-dichlorophenyl 2,5-                                                    diphenyl-1,3,4-oxadiazol-                                                     4',4"-dicarboxylate                                                                             17       18       17                                        Di-4-t-octylphenyl 2,5-di                                                     phenyl-1,3,4-oxadiazol-                                                       3',4"-dicarboxylate                                                                             20       19       18                                        Di-2,5-diphenyl-                                                              3',3",6',6"-tetramethoxy-                                                     1,3,4-oxadiazol-4',4"-                                                        dicarboxylate     19       19       18                                        Di-4-phenylphenyl 2,5-di-                                                     phenyl-1,3,4-oxadiazol-                                                       4',4"-dicarboxylate                                                                             18       17       17                                        Di-3-methylphenyl 2,5-di-                                                     phenyl-1,3,4-thiadiazol-                                                      4',4"-dicarboxylate                                                                             19       19       17                                        Di-4-cyanophenyl 2,5-di-                                                      phenyl-1,3,4-thiadiazol-                                                      1,3,4-thiadiazol-3',4"-                                                       dicarboxylate     19       18       18                                        Di-3-phenoxyphenyl 2,5-di-                                                    phenyl-1,3,4-thiadiazol-                                                      3',3"-dicarboxylate                                                                             20       18       18                                        Di-2,4-di-t-butylphenyl                                                       2,5-diphenyl-3',3"-di-                                                        chloro-1,3,4-thiadiazol-                                                      4',4"-dicarboxylate                                                                             19       17       17                                        Di-3,5-di-t-butyl-4-                                                          hydroxyphenyl 2,5-di-                                                         phenyl-1,3,4-thiadiazol-                                                      4',4"-dicarboxylate                                                                             19       18       18                                        Di-3-methoxyphenyl 1-                                                         methyl-2,5-diphenyl-1,3,4-                                                    triazol-4',4"-dicarboxylate                                                                     18       18       17                                        Di-4-chlorophenol 1-benzyl-                                                   2,5-diphenyl-3',3"-di-                                                        chloro-1,3,4-triazol-                                                         4',4"-dicarboxylate                                                                             20       17       17                                        Di-4-phenylphenyl 1-methyl-                                                   2,5-diphenyl-1,3,4-tri-                                                       azol-3',3"-dicarboxylate                                                                        20       19       16                                        Di-2,4-dichlorophenyl 1-                                                      ethyl-2,5-diphenyl-1,3,4-                                                     triazol-4',4"-di-                                                             carboxylate       17       17       17                                        Di-3,4,5-trimethylphenyl                                                      2,5-diphenyl-1,3,4-                                                           triazol-3',3"-dicarboxylate                                                                     19       17       16                                        ______________________________________                                    

These diesters of bis-heterocyclic aromatic acid compositions findparticular utility as ultraviolet stabilizers in organic compositionsrequiring ultraviolet stability. Such compositions include polymericcompositions such as, for example, polyester fiber and moldingcompositions; poly-α-olefins; polyamides; acrylics; cellulose esters andthe like, as well as molded or shaped articles, film and coatings formedfrom such materials, and the like. Such compositions also includenatural and synthetic rubbers, such as natural rubber, as well asorganic materials such as oils, fats, and unsaturated organic materials,and materials having such materials contained therein, such as paints,varnishes, cosmetics and the like.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:
 1. A synthetic polymer composition susceptible to ultravioletlight degradation stabilized against such degradation with a stabilizingamount of at least one aryl ester of a heterocyclic aromatic acid havingthe formula: ##STR14## wherein A has the structure ##STR15## wherein R₁and R₂ are hydrogen, chloro, bromo, lower alkyl or cyano and are presenton all positions of the benzenoid rings, except the carbon atomsattached to the carboxyl group connecting the heterocyclic aromatic Agroup with the aromatic B group, said carboxyl connecting group isattached to the benzenoid ring in either the meta or para position fromthe carbon atom connected to the heterocyclic ring;B is a group havingthe formula ##STR16## wherein at least one R₃ or R₇ is hydrogen and theother R₃, R₄, R₅, R₆ and R₇ are hydrogen, lower alkyl, lower alkoxy,hydroxy, cyano, chloro and bromo.
 2. A composition according to claim 1wherein the ester has the formula: ##STR17## wherein R₁ and R₂ arehydrogen, chloro, bromo, lower alkyl or cyano; andat least one R₃ or R₇is hydrogen and the other R₃, R₄, R₅, R₆ and R₇ are hydrogen, loweralkyl, hydroxy, cyano, chloro and bromo.
 3. A composition according toclaim 2 wherein the ester has the formula: ##STR18## wherein R₁ and R₂are hydrogen, lower alkyl or cyano; and R₃, R₄, R₅, R₆ and R₇ arehydrogen, lower alkyl, chloro, bromo or cyano.
 4. A compositionaccording to claim 2 wherein the ester has the formula: ##STR19##wherein R₁ and R₂ are hydrogen, lower alkyl or cyano; and R₃, R₄, R₅, R₆and R.sub. 7 are hydrogen, lower alkyl, chloro, bromo or cyano.
 5. Acomposition according to claim 1 wherein the ester has the formula:##STR20##
 6. A composition according to claim 1 wherein the ester hasthe formula: ##STR21##
 7. A composition according to claim 1 wherein theester has the formula: ##STR22##
 8. A composition according to claim 1wherein the ester has the formula: ##STR23##
 9. A composition accordingto claim 1 wherein the ester has the formula: ##STR24##